The Left has traditionally assumed that human nature is so malleable, so perfectible, that it can be shaped in almost any direction. By contrast, a Darwinian science of human nature supports traditionalist conservatives and classical liberals in their realist view of human imperfectibility, and in their commitment to ordered liberty as rooted in natural desires, cultural traditions, and prudential judgments. Arnhart's email address is larnhart1@niu.edu.

Tuesday, December 28, 2010

For many years, I taught a graduate course on the philosophy of the social sciences for students in my political science department. One year, as I was preparing to teach the course, I sent out a survey to all the faculty in the department. I asked them whether political scientists had discovered any general laws of political behavior. And if they believed there were such laws, I asked them to identify the laws. Remarkably, most of those who responded said that there were no such laws. Those who thought there were could identify only a few examples, and the only example that was mentioned more than once was Michels' Iron Law of Oligarchy (the claim that any large organization will tend to be dominated by a few leaders).

This points to an obvious problem. If science is judged by its success in discovering general laws, then political science is not a science. Actually, by comparison with the physical sciences--that apparently have uncovered many general laws of nature--not only political science but all of the social sciences have failed to show any progress at all in formulating and testing general laws of human action. If one agrees with the criteria for science set forth by the logical positivists or logical empiricists in the first half of the twentieth century, the absence of lawlike generalizations in the social sciences shows that they are not really sciences at all.

But doesn't this indicate that in contrast to the physical sciences, the social sciences are similar to the life sciences in their lawlessness? Many biologists and philosophers of biology have noted that there seem to be no laws of biology comparable to the exceptionless laws of the physical sciences. The lawlessness of biology seems to be a consequence of the variability, particularity, contingency, and historicity of living phenomena, which separate the science of biology from physics and chemistry (Beatty 1997; Brandon 1997; Keller 2007). It is possible to formulate a conceptual framework for biology based on well-confirmed generalizations, but these generalizations must allow for the exceptions that arise from the contingencies and variations of life (Scheiner 2010).

I take this as support for the argument that the social sciences can become true sciences by becoming branches of biology. Darwin's theory of evolution by natural selection provides the only general scientific theory that could sustain the social sciences as empirical sciences. This evolutionary theory includes both genetic evolution and cultural evolution as historical processes that include human action. In a Darwinian social science, there would be no general laws, but there would be contingent generalizations holding true for greater or lesser periods of time (Rosenberg 1980, 2007).

So, for example, what I have identified as the 20 desires of evolved human nature might be true for most of human evolutionary history. But the cultural evolution of liberal capitalism might depend on the historical contingencies of the last two centuries. Moreover, within the constraints of natural history and cultural history, human individuals will exercise judgment about what is best for them in their particular circumstances. Within such an evolutionary framework, we can explain and predict intentional human action as caused by human beliefs and desires, but our explanations and predictions will never have the certainty or precision attainable through the general laws of the physical sciences.

As an illustration of this Darwinian social science, we could explain Abraham Lincoln's decision to issue the Emancipation Proclamation as shaped by the universal political history of the human species, the cultural political history of the American regime, and the individual political history of Lincoln. This would be similar to the kind of scientific explanation of animal behavior that we see in the work of primatologists like Frans de Waal or Jane Goodall, who explain the behavior of their chimpanzees as showing the unique life history of each individual chimpanzee, the natural history of the species, and the cultural history of the group.

Thursday, December 23, 2010

This Christmas, my wife and I will be giving one of our little nieces furniture for her doll house. Are we reinforcing the sexist stereotypes of our culture? Or are we rightly judging that this is her natural preference, and that it's different from her brother's preference for toys?

Why is it that little girls are more inclined to play with dolls, while little boys are more inclined to play with trucks and toy weapons? Some people say this is purely cultural, and so if the cultural practices were different, we could teach our little girls to throw away their dolls and play with trucks and guns. Others see this as showing a naturally innate difference, because girls tend to have a greater interest in caring for infants.

Remarkably, a similar nature-nurture debate must now be extended to chimpanzees. Sonya Kahlenberg and Richard Wrangham have written an article reporting a sex difference in the use of play objects among chimpanzees in Kibale National Park, Uganda, and the difference matches the human case.

Juvenile chimpanzees in this group tend to carry sticks in a way that suggests they're playing with dolls, and this is more common among females than among males. Female chimps are more likely than males to care for infants, and when a female becomes a mother, she no longer carries stick-dolls, because now she has the real thing. So carrying the stick-dolls seems to be a form of play-mothering.

But while the greater female interest in infant care has been observed in all chimpanzee groups, this pattern of play-mothering with sticks has not yet been reported for any group except those in Kibale. So this seems to be an example of chimpanzee culture. This group in Kibale has a cultural tradition of stick-doll play.

Is this nature or nurture? Or some combination of both? There seems to be some kind of social learning. But it's not that the females are learning this from their mothers, because mothers don't play with the stick-toys. So if it is socially learned, the youngsters are learning it from one another.

Here, then, is another illustration of how the complex interaction of natural inclination and social learning that we see among human beings can also be seen among our primate relatives.

Sunday, December 19, 2010

One of my graduate students--Paul Vasholz--is writing a dissertation that argues for the compatibility of free will with modern neuroscience. In developing his argument, he builds on the work of Walter J. Freeman, a neuroscientist who defends the reality of human freedom, while also showing how neuroscience supports Thomas Aquinas's philosophical psychology.

Freeman's research has led him to formulate what he calls "nonlinear brain dynamics" as an alternative to the linear causality that is assumed in much neuroscientific research. Moreover, he argues, this nonlinear brain dynamics supports Aquinas's teaching about the unity of mind, brain, and body. Freeman's position catches my interest, because it seems to sustain my argument about the emergent evolution of the soul in the brain and the freedom of the human soul as the product of that emergent evolution.

For Freeman, the key question is whether perception is passive or active. While Plato views perception as a passive acceptance of eternal forms or ideas, Aristotle views perception as an active exploration of the world. Aquinas follows Aristotle in explaining perception as an active process of assimilation. The body does not absorb stimuli, but rather it changes its own form to grasp those aspects of the stimuli that are relevant to the goals in the brain. Knowledge is not driven by external powers, as suggested by Plato, but rather knowledge is driven by the brain's internal strivings and ends, as we explore the world and, by trial and error, assimilate ourselves to our physical and social world in a manner that satisfies our desires.

But then where do these self-generated actions into the world--our strivings to search and observe the world--come from? Aquinas's answer is that the ultimate source of our striving is nature and nature's God. Freeman's answer is that the ultimate source is natural evolution. Through evolutionary history, human beings have inherited a natural set of desires or inclinations that guide their intentional behavior.

I agree with Freeman that there is much in Aquinas's philosophical psychology that supports this understanding of the emergent evolution of the soul or mind as the activity of the brain. But Freeman fails to confront the incoherence in Aquinas's reasoning on this point, which manifests a fundamental problem in Aquinas's Aristotelian science of human nature. This is not just a problem for Aquinas, but a general problem in reconciling Biblical religion and evolutionary science. (See Freeman's "Nonlinear Brain Dynamics and Intention According to Aquinas," pp. 211-12, 211, 230-31, 233.)

The problem is the incoherence in both affirming and denying a radical dualism of body and mind. On the one hand, Aquinas agrees with Aristotle's biological psychology that the mind is the form of the living body, and thus mind and body are inseparable, so that the death of the body is the death of the mind. On the other hand, Aquinas's commitment to the Christian teaching about the afterlife forces him to say that the human mind or soul is immaterial and thus capable of existing without the living body supporting it. The situation becomes even more confusing when we see that Aquinas's commitment to the Christian teaching about the resurrection of the body forces him to say that the human mind or soul cannot exist in its perfection unless it is the activity of a living body.

Aquinas recognizes that in adopting Aristotle's biological psychology, he has to reject Plato's dualistic psychology. For Plato, the immortal soul rules over the mortal body like a pilot of a ship, and thus the soul can live on after the death of the body. Many early Christians (like Augustine) saw this Platonic dualism as the closest pagan approximation to Christian theology. After all, Plato's dialogues offer elaborate arguments for the immortality of the soul in an afterlife with eternal rewards and punishments. Plato's Timaeus looks enough like Biblical creationism that it became the primary text for medieval Christian cosmology. And yet orthodox Christians cannot be Platonic dualists, because Christians must believe in the resurrection of the body in the afterlife, which suggests that the perfection of the soul depends on the body. Moreover, Aristotle's criticism of Plato's theory of the eternal Ideas, with its dualism of mind and body, and Aristotle's teaching that the mind is the functional activity of the body denies Platonic dualism.

To defend the doctrine of the resurrection of bodies to eternal life, Aquinas thinks he needs to reject Platonic dualism and embrace Aristotelian mind-body unity. But it's not at all clear that an Aristotelian biological psychology can allow for living bodies to become immortal. Moreover, traditional Christian doctrine teaches that there's a period between death and resurrection in which human souls exist without bodies, just as angels exist without bodies. But it's hard to see how this is reconcilable with the inseparable unity of mind and body.

Aquinas is thus caught in a contradiction. He must say that "the soul is the form of the animated body," and "forms dependent in being upon matter do not themselves have being properly, but being properly belongs to the composites through their forms" (Summa Contra Gentiles, II, 51, 57). This would be compatible with neuroscientific research showing that the mind is the emergent activity of the brain. But then Aquinas also says that the human mind is an immaterial form that is not necessarily the form of a living material body. This suggests a radical dualism contrary to neuroscience.

The confusion is deepened, however, when Aquinas teaches that since "the soul is united to the body as form to matter," the perfection of the soul after the death of the body requires a resurrection of the body and its reunion with the soul. Thus must be so, because "the state of the soul in the body is more perfect than outside the body" (Summa Theologica, suppl., q. 75, a. 1).

Furthermore, according to Aquinas, this resurrected body must be a real living body. And since all living bodies are ageing bodies, the resurrected bodies must have a specific age. Since Jesus rose again at about age 30, that age must be the perfect age for the body, and so, Aquinas reasons, when human beings are resurrected, they will all have bodies of the same age--30 years old. Those who died as children will be moved up to age 30, and those who died in old age will be moved back to age 30 (ST, suppl., q. 81, a. 1).

But then we must wonder, when people wish for immortality, is this what they're wishing for--to be frozen eternally at one moment in time?

Tuesday, December 14, 2010

From Aristotle to Darwin to E. O. Wilson, how one understands human morality and politics seems to depend on how one understands the social insects. The importance of this line of thought in explaining social evolution has recently been highlighted by Wilson's attack on kin selection theory and his defense of Darwin's group selection theory in explaining social evolution from insects to humans.

To explain the biological nature of human beings as political animals, Aristotle compared human beings to other political animals--and particularly, ants, bees, and wasps. The great size and complexity of social insect colonies are comparable to that of human communities.

Darwin saw the same resemblance between human communities and social insect colonies--particularly, in their intricate division of labor. But for Darwin, the existence of sterile female castes of workers among the social insects was "by far the most serious special difficulty which my theory has encountered," as he wrote in the chapter on "Instinct" in The Origin of Species. The obvious problem is that this seems to contradict evolution by natural selection, because the sterile females are sacrificing their reproductive fitness for the reproductive advantage of the queen. Darwin's solution was to propose that "selection may be applied to the family, as well as to the individual, and may thus gain the desired end." He thus implied that natural selection could favor the altruistic sacrifice of individuals for the reproductive good of their group. Moreover, in The Descent of Man, he clearly claimed that human moral and political evolution depended on group selection in war, so that some of the highest moral virtues arose as dispositions that conferred advantages on human groups in violent conflict with other groups. But he left it unclear as to how exactly natural selection could do this.

In the 1960s, William D. Hamilton set out to solve Darwin's problem by developing the ideas of "inclusive fitness" and "kin selection." The basic idea is that individuals can evolve to show altruistic behavior--behavior that is costly to the animal but beneficial to others--if the cost to the actor brings sufficient benefit to sufficiently closely related recipients. Evolutionary selection should favor my acting not only for the sake of benefiting my direct offspring, who share some of my genes, but also for benefiting the offspring of my close relatives, who share some of my genes and therefore might carry my genes for altruistic behavior. In the case of sterile female worker castes, Hamilton argued, this extraordinary altruism could be explained by the fact that the workers are sisters who are more closely related genetically to one another that they are to their offspring, and consequently, it better enhances their inclusive fitness to serve the reproductive activity of the queen in producing more sisters than to have offspring of their own. This happens because among the Hymenoptera, the order of ants, bees, and wasps, the sex-determining mechanism is haplodiploidy, in which fertilized eggs become females, and unfertilized eggs males.

There are serious problems with this theory. One is that some of the eusocial species--such as termites and naked mole rats--don't use haplodiploid sex determination, and therefore Hamilton's theory can't explain the sterility of worker castes among them as it does for Hymenoptera.

But despite such problems, Hamilton's theory of kin selection has been widely accepted among many biological theorists of social evolution over the past 50 years, and especially since the publication of Wilson's Sociobiology in 1975, which adopted Hamilton's theory.

In recent years, however, E. O. Wilson and David Sloan Wilson have been criticizing kin selection theory and defending group selection theory as superior. Most recently, E. O. Wilson co-authored an article with Martin Nowak and Corina Tarnita in Nature (vol. 466, August 26, 2010, pp. 1057-1062) that summarizes some of the reasoning against Hamilton's theory. This article has provoked an intense controversy in the whole community of biologists and psychologists studying the biological evolution of sociality.

Much of the publicity surrounding this controversy turns on the perception that E. O. Wilson has undergone a radical change of mind--from promoting to rejecting Hamilton's theory. But anyone who reads Wilson's Sociobiology carefully (for example, pp. 30, 129) will see that he was never convinced that Hamilton's theory was superior to group selection theory. Over the years, Wilson has given encouragement to proponents of group selection such as David Sloan Wilson; and in recent years, the two Wilsons have co-authored some articles.

It's hard for me to see that one has to choose between kin selection and group selection in explaining social evolution. I suspect that this is a false dichotomy that obscures their complementarity. In fact, one can even argue that kin selection is a form of group selection where the group is constituted by kinship. Here I agree with Samir Okasha, who makes the argument for complementarity in a recent article in Nature (vol. 467, October 7, 2010, pp. 653-55.)

Regardless of whether one favors kin selection, group selection, or some combination of both, there is a deeper moral and political issue here. All of these kinds of Darwinian explanations of social evolution point to the inevitability of tragic conflicts in moral and political life that cannot be resolved by ideal principles of universal love and cooperation.

There is a tendency among modern moral and political philosophers to assume that moral and political life can and should be governed ultimately by some ideal conception of disinterested humanitarianism. One can see this, for example, in John Rawls' appeal to the ideal situation of people agreeing to universal, rational principles of justice in the "original position," where human beings would act as if they were disembodied spirits. One can also see this among religious believers who assume that the teaching of universal love in Jesus' Sermon on Mount is the moral ideal for all human beings, or among secular philosophers like Peter Singer who assume that morality and politics should be guided by an impartial concern for the interests of all sentient creatures.

If our moral and political dispositions have not been created by some cosmic order of the good and the just to conform to some eternal values of love and cooperation, if these dispositions have been created, on the contrary, by natural evolutionary selection, then we can expect that our moral and political lives will be torn by tragic conflicts of interest that cannot be resolved by universal principles of ethics.

E. O. Wilson refers to this as the problem of "moral ambivalency," and it runs through his writing in his book Sociobiology, beginning with the epigram from the Bhagavad Gita. The passage Wilson quotes shows Arjuna doubting the justice of leading his family in a war against another family competing for political dominance, but Lord Krishna (the Lord of the Universe) teaches him that this is his sacred duty. Wilson suggests that an evolutionary theory of social evolution would explain this tragic conflict as arising from a natural history of counteracting pressures on the units of natural selection. Wilson writes:

What is good for the individual can be destructive to the family; what preserves the family can be harsh on both the individual and the tribe to which the family belongs; what promotes the tribe can weaken the family and destroy the individual; and so on upward through the permutations of levels of organizations. Counteracting selection on these different units will result in certain genes being multiplied and fixed, others lost, and combinations of still others held in static proportions. According to the present theory, some of the genes will produce emotional states that reflect the balance of counteracting selection forces at the different levels. (p. 4; cf. pp. 129, 563)

Here, then, is the scientific basis for the tragic realism of evolutionary ethics. We see the evolved moral and political nature of human beings as shaped by countervailing levels of selection, which have created tragic conflicts in our moral emotions that cannot be resolved by rational appeals to universal moral principles. Such moral realism is repugnant to moral utopians who assume that moral and political order must be ultimately guided by universal rules of love and cooperation that can in principle resolve all conflicts.

Oddly enough, while E. O. Wilson accepts this moral realism as a conclusion from his evolutionary account of morality as shaped by group selection, David Sloan Wilson rejects this conclusion while trying to hold on to some utopian vision of universal cooperation.

Wednesday, December 08, 2010

As I look back on my graduate seminar on Aristotle this semester, one point stands out: how one interprets Aristotle's Nicomachean Ethics depends crucially on whether one sees the peak of the book in the account of friendship in Books 8 and 9 or in the arguments for the supremacy of the philosophic life in Book 10.

If Book 10 is the peak, then one will see the whole book ascending steadily to the teaching that the contemplative life of philosophy is the highest good, because it is the activity of the intellect as the most divine part of human beings. The moral virtues and practical reasoning will be seen as inferior to the intellectual virtue of philosophy as the dominant end or summum bonum for all human beings. Since most human beings cannot live a philosophic life, they are condemned to live a less than fully human life.

This leads one to conclude that the best moral and political order would be ruled by, or at least in the service of, philosophers; and this moral and political order would conform to the cosmic order of the universe as ruled by the divine Mind and the eternal Ideas.

This reading of the Ethics would assume that Aristotle's ethical teaching is ultimately Platonic in its conformity to the moral and intellectual cosmology of Plato or Plato's Socrates, particularly in Plato's Republic and Timaeus. This Platonic Aristotelianism would contradict my argument for the biological character of Aristotle's reasoning and the compatibility of this biological Aristotelianism with Darwinian science.

In contrast to this reading, if one sees the peak of Aristotle's Ethics in his books on friendship, then one will see the Platonic arguments for the philosophic life as a solitary and divine life of pure intellect as dubious, because these arguments contradict what Aristotle teaches in Books 8-9 about the natural sociality of human life and the primacy of friendship as rooted in human biology.

The philosophic life does appear in Books 8 and 9. But here it appears as activity that is cultivated by friends as a social activity of those who find their deepest existence in philosophizing together with their friends. By contrast, the word "friendship" (philia) never appears in the Platonic account of philosophy in Book 10, which depicts philosophy as a life of god-like solitude separated from social life. The only concession to social activity in Book 10 is that the philosopher is said to perhaps benefit from having "co-workers."

In Books 8 and 9, philosophy as an activity of friends is activity of embodied minds in social interaction, which can be explained biologically as an activity of human beings as rational and political animals by nature.

And while Book 10 suggests a dominant end conception of the human good, in which all goods are ranked below philosophy, Books 8 and 9 suggest an inclusive end conception of the human good, in which philosophy is one good among many. The thought here is that different human beings will rank the natural human goods in different ways to conform to their natural temperament and their social circumstances.

At the end of his account of friendship, Aristotle writes:

Is it then the same way with friends as with lovers, for whom seeing the beloved is their greatest contentment, and the thing they choose over the other senses, since it is especially through seeing that love is present and comes to be present, so that for friends too, living together is most choiceworthy thing? For friendship is a sharing in common, and one has the same relation to a friend as to oneself, while in relation to oneself, the awareness that one is is something choiceworthy, and thus it is so in relation to the friend as well; but the being-at-work of this awareness comes about in living together, and so, naturally, friends aim at this. And whatever being existence consists in for any sort of people--whatever it is for the sake of which they choose to be alive--this is what they want to be engaged in with their friends. This is why some friends drink together, others play dice together, and still others engage in athletic exercise together and go hunting together, or engage in philosophy together, each sort spending their days together in whatever it is, out of all of the things in life, that they are most contented by; for since they want to share their lives with their friends, they do those things and share those things that they believe living together consists in. (1171b29-72a8)

One can see here why Douglas Rasmussen and Douglas Den Uyl look to Aristotle's study of friendship as supporting their Aristotelian defense of liberalism. It seems that although the generic goods of life are universally the same for all human beings by virtue of their human nature, the ranking and organization of those generic goods is individualized for the life of each human being. Moreover, this pluralism of good lives is cultivated in civil society, where moral character is shaped through natural and voluntary associations.

Saturday, December 04, 2010

In 1971, East Pakistan became Bangladesh after winning a 9-month war of independence from West Pakistan. Shortly after the end of the war, Malcolm Potts led an international team of doctors into Bangladesh to help the women who had been raped and made pregnant. They offered abortions to the women. In a conservative Muslim society, women who have been raped are shunned as unclean by their families and society generally. To have an abortion only adds to their humiliation. Over 100,000women were raped during the conflict, which made it perhaps the largest systematic rape of women in the history of the world.

The horror of this experience--and of similar experiences with warfare--led Potts to want to explain the cruelty of organized aggression in human history. The final product of his thinking is his book (co-authored with Thomas Hayden) entitled Sex and War: How Biology Explains Warfare and Terrorism and Offers a Path to a Safer World (BenBella Books, 2008).

Reading this book in my course on "Biopolitics and Human Nature" has stirred a lively discussion among the students.

THREE THESES

Potts offers an evolutionary explanation for the causes of war and terrorism and for how such violence can be reduced. His argument turns on three claims.

His first claim is that young men have an evolved predisposition to "team aggression," which he identifies as the intentional coordination of young males in launching lethal attacks against members of their own species. He believes that there are only two species of social mammals showing this behavior--human beings and chimpanzees--and he explains this as showing an evolutionary history in which humans and chimps shared a common ancestral species in which young males practiced team aggression.

The primary insight for this claim came a few years after the war in Bangladesh, when Jane Goodall observed the chimps in the Gombe Stream National Park in Tanzania waging a war between two chimp communities, in which young males organized themselves into raiding parties to attack individuals in the opposing community. Through a series of ferocious attacks, the Kasakela troop eventually conquered the territory of the rival Kahama troop.

Potts offers various kinds of arguments and evidence to support his claim that such team aggression among young males has shaped human evolution. There is fossil evidence that many hominid ancestors died from warfare. There is archaeological evidence that warfare is pervasive in human history. And there is anthropological evidence that foraging bands (like the Yanomamo, for example) have engaged in such team aggression. Moreover, there is also evidence for the "warfare hypothesis" in explaining human evolution as shaped by group-against-group violence that drove the evolution of human intelligence, religion, and state-formation.

Potts' second claim is that women do not have this evolved predisposition to team aggression. Of course, women are capable of aggressive violence. But they do not generally organize themselves into raiding parties for lethal violence against their enemies.

This leads to his third claim, which is that the best way to promote peace is to empower women so that their peacemaking tendencies can counter the warmaking tendencies of men. To achieve that, women need to have equal access to political power, and they need to have control over their lives.

Most importantly, women need to have freedom in controlling their reproduction through family planning, which requires access to contraception and abortion. If women are free to choose how many children they will have, Potts believes, they will generally choose to have small families. This will increase their social and political influence, because this will lessen the burdens of child care. This will also slow population growth, which will have the advantage of reducing the number of young males in proportion to older males, which reduces the likelihood of young male violence.

Potts is a life-long proponent of family planning. In 1968, he became the first doctor employed on the staff of the International Planned Parenthood Federation. This has led him to travel around the world promoting family planning.

He argues that family planning is the key to reducing population growth, which is the key to reducing war and terrorism. In over-populated societies, there are too many young males who lack economic resources and who cannot find sexual mates, which creates conditions favoring young male team aggression. Potts thinks this is evident in the societies that foster terrorism. Terrorists tend to be young, unmarried males with few opportunities for success in life, who become vengeful towards dominant outgroups, and who band together to attack their enemies.

I have identified courage in war as one of the 20 natural desires that shape human nature in all societies throughout history. That's the one desire on my list that has provoked the most criticism from people who don't like the idea that war is natural for human beings and a stage for the moral virtue of courage. While I have never written enough to support my evolutionary view of war, Potts' book provides a good survey of the reasoning and evidence for war as a natural desire--particularly, among young men--that manifests both the best and the worst in human beings.

But despite my general agreement with Potts, I do see at least eleven problems with Potts' position.

ELEVEN PROBLEMS

(1) THE NATURAL MALE INHIBITION AGAINST KILLING. Most men will never kill anyone. In most men, there probably is a natural inhibition against killing. Even soldiers in war are often reluctant to kill the enemy, which is why special training is required to break down this inhibition. This point is elaborated in Dave Grossman's book--On Killing--which surveys the psychology of killing in war.

But if there is such a natural inhibition against killing, then how can Potts argue that young men are predisposed by their evolved nature to team aggression? Potts' answer is that evolution has given us an "empathy switch," so that "we seem to have an innate mental ability to treat our fellow humans with either great compassion or cold disregard, depending on whether we've assigned them to ingroup, or out" (70). The difference between men and women is that for young men, on average, it's easier to turn off the empathy switch when they think they're confronting an outgroup.

(2) VIOLENT WOMEN. Potts notes the many historical examples of female violence in war. There are female suicide bombers and "warrior Amazons." Women have fought in military units. And in the American military, women are taking ever larger roles that take them into combat. Although this might seem to deny Potts' claim about sex differences in team aggression, he can answer by arguing that women engaging in team aggression are exceptional cases. We might see the behavioral profiles of men and women as two overlapping bell-shaped curves, so that despite the overlapping, we can still see the difference in their central tendencies.

(3) THE BONOBO PROBLEM. Of the four extant great ape species--gorillas, orangutans, chimpanzees, and bonobos, chimps are the only species that shows male coalitional violence like that of human beings. The contrast is especially evident with bonobos, who have never been observed engaging in lethal violence, and who seem to show a "make-love-not-war" policy enforced by the females banding together to dominate over the males. That's why some feminists and pacifists suggest that if bonobos are closely related to humans, this should deny the claim that human violence is an evolved trait.

It's not clear to me that Potts has an adequate answer to this. He asserts that "team aggression died out in bonobos, while persisting in Pan troglodytes and Homo sapiens" (129). But this remains mere speculation. The problem here is that there is too little known about bonobos to reach clear conclusions on this issue.

(4) CULTURAL CIRCUMSTANCES. The most common criticism of Potts is likely to be that his biological explanation of war and terrorism does not recognize the importance of cultural circumstances in shaping violent behavior. But, actually, Potts emphasizes that while the behavioral predisposition to team aggression is an evolved trait of men, the expression of that predisposition is determined by economic and social circumstances. So, for example, when there is a high proportion of young males in a society who lack resources and lack access to sexual partners and feel resentment towards a dominant outgroup, this is a social breeding ground for terrorism or street gangs. Consequently, we can control the predispositions to some degree by controlling the circumstances.

(5) THE NOVELTY OF MODERN WAR. Modern military organizations don't look much like the raiding parties of chimps or human foragers. It was not until the emergence of the state as based on an agricultural economy about 5,000 years ago that mass armies were made possible, and this is too recent in human history to be a biological adaptation.

Potts' answer to this objection is that even modern armies are based on small units--squads (9-15 men) and platoons (45-70 men)--because the the psychology of team aggression still requires that young men see themselves as a "band of brothers" with a sense of camaraderie that can only arise in small units comparable in size to a chimp raiding party. This is true even though modern bureaucracy allows these small units to be organize hierarchically into massively large military organizations.

(6) SANGER AND EUGENICS. As a proponent of family planning, Potts sees himself in the tradition of Margaret Sanger, who was the founder of the modern family planning movement. But in his praise of Sanger, he is silent about her dark side: she was a proponent of eugenics and sterilization for the "unfit." Although this might seem like a minor point, it's important as an indication of Potts' failure to be candid about the historical connections between family planning and eugenics.

(7) THE BREEDING OF FUNDAMENTALISTS. Potts is disdainful of religious belief, and particularly, fundamentalist religious belief, because he see religious fundamentalism as opposed to modern science, which is, for him, the voice of reason in the world. But there's a problem here that he doesn't acknowledge. He likes to think that modern scientific rationalism will prevail in its battle with religious fundamentalism. And yet, he notes that religious believers tend to have much higher birth rates than secular people. If that's the case, doesn't that mean that eventually fundamentalist religious believers will prevail, just by virtue of their greater growth in population? Potts never confronts this problem for his argument.

(8) THE JULIAN SIMON PROBLEM. Potts' argument for family planning to reduce population is based on the reasoning of Thomas Malthus that population growth must lead to a social collapse from the exhaustion of scarce resources. Malthusian doom pervades Potts' book, because he sees all of life as governed by competition over scarce resources. In taking this position, Potts never confronts the serious criticisms of the Malthusian view of the world. In particular, Potts never explicitly responds to the arguments of those like Julian Simon who insist that, on the whole, population growth is more a boon to humanity than a burden, because human beings add to resources through their productivity and their ingenuity. In his book The Ultimate Resource, Simon showed how the data of history refute the gloomy predictions of the Malthusians.

As far as I can see, there is only one paragraph on this point in Potts' book. He writes:

Free-market economists make up yet another important force from the right, arguing that population growth is good because growing markets create prosperity. They tend to believe that as young people reach working age they will contribute to the economy, even though the empirical evidence, as we have seen, is that in countries with rapid population growth young people merely join the lines of the unemployed. Many economists also claim that natural resource scarcities can be compensated for by technologies and price adjustments, and they too have been influential in reducing U.S. political interest in international family planning assistance. (327)

This is all he has to say. He is silent about the extensive evidence provided by Simon (and by others like Bjorn Lomborg and Matt Ridley) supporting the claim that when markets are free, population growth is generally beneficial.

Potts should at least say something about Simon's famous bet with Paul Ehrlich. In 1980, Simon bet Ehrlich $10,000 that the prices of a list of scarce metals would be lower by 1990, while Ehrlich predicted that the growing scarcity of these metals would produce much higher prices. Simon won the bet.

(9) STONE AGE EMOTIONS. Potts shows how "Stone Age emotions" govern politics. For example, he argues, the "war on terror" as a response to the 9/11 terrorist attacks was an irrational expression of those "Stone Age emotions." The wars in Afghanistan and Iraq were not in the national security interests of the United States. But they were justified by President Bush who appealed to the natural emotional predisposition to team aggression in response to threats from a dangerous outgroup. Instead of yielding to such emotions, Potts claims, we should act by a "cool, objective analysis of risk" like a "dispassionate super computer" (174).

But how is this possible, if "an unemotional response is impossible" (113)? Although Potts often recommends that pure, dispassionate reason should suppress our "Stone Age emotions," he also says that we need to extend our evolved emotions of empathy from the ingroup to the outgroup (166-67, 238, 258). Moreover, in a few passages, he agrees that "the building blocks of human morality are emotional as well as cognitive" (361). Isn't it more realistic to appeal to the moral emotions of empathy, while extending them to ever wider groups, than to try to totally suppress the emotions under some dispassionate Kantian Reason? Isn't this extension of empathy (or "sympathy" as Hume, Smith, and Darwin called it) the psychological basis for "human rights" and humanitarian concern? This would seem to be more compatible with Darwin's view of the moral sense based on sympathy and with the moral psychology of the emotions developed by Darwinian psychologists today.

(10) THE JUSTICE OF MALE HONOR. Potts gives some attention to the historical movements for abolishing slavery, for standards of just war, and for humanitarian conceptions of human rights, which have put some limits on the cruelty of war. But he does not comment on the fact that these movements have been led by men as well as women. Doesn't this show that the extension of empathy beyond narrow ingroups can be rooted in male moral psychology? Can't we see the traditional standards of just war as expressions of the manly love of honor and the desire to elevate warrior honor above brutish cruelty? If so, then this shows how the taming of manly aggression might come not just from womanly compassion but also from manly chivalry.

(11) THE MANLY HUMANITARIANISM OF SCIENCE. Potts appeals to modern science as promoting a cosmopolitan community of rational understanding that can check the parochial predispositions of male team aggression. He writes: "Science, with its intrinsic honesty and its rejection of the supernatural as an answer to real world events, has proved the only medium in history capable of linking women and men of all cultures and all races in a common understanding of the real world" (360). But Potts doesn't ponder the fact that, for most of its history, modern science has been dominated by men. Doesn't this show another way in which the natural dispositions of some men--in this case, the Socratic desire for intellectual understanding--can be turned against male violence?